It is recognized that cigarette smoking is a common risk factor for the development of cancers of the lung, larynx and oral cavity. Although "pre-neoplastic" lesions are identified for these smoking related cancers, not all lesions become malignant and currently there is insufficient evidence to determine which features reliably predict malignant potential of such lesions. We hypothesize that the conventional histopathological examination of pre-neoplastic" lesions provides insufficient information on prognosis, but genetic and epigenetic alterations in these lesions may provide valuable information in this regard. It is also important to focus on molecular alterations, which can be detected in 'pre-neoplastic" lesions and could be clinically targeted with minimum adverse effects, since primary prevention of smoking related cancers by elimination of tobacco abuse may not be a realistic goal for everyone. We propose that alterations in global DNA methylation in "pre-neoplastic" lesions is an important epigenetic change to be validated because of its significance in the process of carcinogenesis and the possibility of changing its status by nutritional intervention. The primary hypothesis to be tested in this proposal is that global DNA methylation status in 'pre-neoplastic" lesions (hyperplasia, metaplasia, dysplasia and CIS) of the human lung, larynx and oral cavity of subjects who have not developed cancers is higher compared to the methylation status of the same "pre-neoplastic" lesions detected in subjects who have developed cancers. To test this hypothesis, a retrospective follow-up study will be conducted with subjects who were diagnosed with a "pre-neoplastic" lesion of the lung, larynx or oral cavity. Subjects who have been followed clinically for at least three years will be studied. Those who developed an incident cancer vvill be compared to those who did not, with respect to the degree of global methylation of DNA of the 'pre-neoplastic" lesions diagnosed at the baseline. A newly developed and tested immunohistochemical technique, which measures the degree of global methylation in intact and specific types of cells, will be used to evaluate global DNA methylation in the proposed study.